The information that generally appears in the form of alphanumerical characters on an LCD display, or in an aperture cut into the dial, to give complementary information to the current time, such as the date, the month or the day of the week, or even non time-related information such as the ON/OFF state of a function. In this latter case, this information is carried by discs or rings driven by the timepiece movement and are formed by successions of alphanumerical signs or pictograms of small dimensions, with the exception of course of “large date” devices, which have the drawback of relying on a bulkier, more complicated and therefore more expensive mechanism.
In order for the user to be able to read the displayed information better, designers have imagined for a long time placing a magnifying glass above the information to be read. By way of example, one can cite JP Patent No. 62014083 in which a convex lens is provided in the dial on an LCD display, said dial further comprising an analogue display using hands. In JP patent No 61205889, the magnifying device is formed by a magnifying ring formed in the external part of the crystal. The magnifying device can also be provided in the internal face of the crystal by adding a lens in a housing provided for this purpose, as disclosed in EP Patent No. 0 814 388 or by machining said lens in the internal face of the crystal, as disclosed for example in U.S. Pat. No. 6,406,769.
All of these magnifying devices magnify the information carried by the display, making it more visible, but necessarily induce distortions that may be more or less significant. It is known to correct such distortions, for example in cameras, using a stack of corrective lenses, as disclosed for example in US Patent No 2003/0189760. In a timepiece, given the small space available between the dial and the crystal and the probable occupation of such space by hands, it is not possible to envisage performing this optical correction by means of such a lens stack.